The present invention relates to wiper devices that wipe vehicle windows.
A wiper device of a vehicle includes a wiper arm attached to a pivot shaft. The pivot shaft pivots the wiper arm in a predetermined angular range to wipe a window.
Japanese Unexamined Patent Publication No. 8-156747 discloses a module type wiper device with a pair of wiper arms that move synchronously. This wiper device includes a pair of pivot holders each of which support a pivot shaft. A pipe frame connects the pivot holders to each other. The wiper arms are attached to the associated pivot shafts.
The pivot holders are secured to opposite ends of the pipe frame through caulking. More specifically, as shown in FIGS. 8 and 9, each pivot holder includes a fitting portion 110 that is fitted in a pipe frame 100. Eight recesses 111, as a whole, are formed in the outer side of the fitting portion 110. That is, four recesses 111 are spaced from the remaining four recesses 111 at predetermined intervals in an axial direction of the fitting portion 110. Each recess 111 forms a pair with one of the recesses 111 that are axially spaced.
A pair of press dies 120 with a plurality of pressing portions 121 that correspond to the recesses ill are prepared. After the fitting portion 110 is fitted in the pipe frame 100, the pressing portions 121 of each press die 120 press the outer side of the pipe frame 100. This deforms a portion of the pipe frame 100 that corresponds to each recess 111 such that the deformed portion enters the recess 111, thus securing the pivot holder to the pipe frame 100.
As shown in FIG. 9, the two corresponding recesses 111 that are spaced from each other in an axial direction of the fitting portion 110 each have a side wall 111a. The side walls 111a of these recesses 111 face in opposite directions and are parallel with each other. Further, as shown in FIG. 8, the two corresponding recesses 111 adjacent to each other in a circumferential direction of the fitting portion 110 each have a side wall 111b. The side walls 111b of these recesses 111 face in opposite directions and are parallel with each other. The side walls 111a, 111b are parallel with a movement direction of each press die 120. In addition, if the pivot holder is formed using a pair of separate molds through aluminum die casting or the like, the molds must be separated from each other in a direction parallel with the side walls 111a, 111b for isolating the pivot holder from the molds. However, it is complicated to design and fabricate the molds such that a separating direction of each mold is precisely parallel with the side walls 111a, 111b. Further, the designing of the molds is restricted.
To reliably stop the pivot holder from becoming loose with respect to the pipe frame 100, a caulking portion of the pipe frame 100 must be in secure contact with the inner wall of each recess 111. As shown in FIG. 9, a cross-sectional shape of each recess 111 in an axial direction of the fitting portion 110 is rectangular. That is, a corner portion of the inner wall of each recess 111 (in FIG. 9, a corner portion between each side wall 111a and the bottom of the recess 111) is relatively squared The corner portions of each pressing portion 121 thus must be relatively squared to ensure that the caulking portion of the pipe frame 100 is in secure contact with the inner wall of each recess 111. In this case, when each pressing portion 121 plastically deforms the pipe frame 100, reactive force may act focally on a portion of the pipe frame 100 that corresponds to each corner portion of the pressing portion 121, thus causing a crack. Further, the corner portions of each pressing portion 121 quickly wear, and a desired securing strength of the pressing portion 121 is hampered at an early stage.
In a wiper device disclosed in Japanese Unexamined Patent Publication No. 5-32153, two pivot holders are each secured to an end of a pipe frame through a bolt. Each pivot holder has a shaft hole that receives a pivot shaft and a through hole through which the bolt is passed. The axis of the shaft hole is parallel with the axis of the through hole. In this case, each pivot holder can be isolated from a pair of molds, which form the pivot holder, by separating the molds from each other along the axis of the shaft hole and the axis of the through hole, when molding is completed. In other words, the molds must be designed and fabricated with high accuracy such that a movement direction of each mold, the axis of the shaft hole, and the axis of the through hole are completely parallel with one another. Like the prior art shown in FIGS. 8 and 9, this complicates the fabrication of the molds and restricts the designing of the same. Further, as long as the axis of the shaft hole is parallel with the axis of the through hole, the pivot holder cannot be generally used. In addition, it is troublesome to secure each pivot holder to the pipe frame through the bolt.
Accordingly, it is an objective of the present invention to provide a wiper device that enables a pivot holder to be secured to a pipe frame easily and reliably and allows the pivot holder to be manufactured with a reduced cost.
To achieve the above objective, a wiper device according to the present invention includes a pair of pivot holders each including a fitting portion that extends along a fitting axis, a pivot shaft that is rotationally supported by each pivot holder, and a frame that connects the pivot holders to each other. A plurality of recesses are formed in an outer side of each fitting portion. A wiper arm is secured to each pivot shaft. A receiving portion in which each fitting portion is received is formed at each end of the frame. The receiving portions are subjected to caulking with the fitting portions received in the corresponding receiving portions, such that a portion of each receiving portion that corresponds to each recess enters the recess. Each recess includes a curved bottom and a curved open end. Regarding each pivot holder, an angle between a normal line that corresponds to a maximum depth portion of each recess and a tangential line that corresponds to the open end of the recess is defined as an open angle. Further, an angle between the axis of the corresponding pivot shaft and the normal line is defined as a shaft angle. In this case, each recess is shaped and located such that the open angle is constantly greater than zero and equal to or greater than the shaft angle, as viewed along any cross-sectional plane that includes the normal line.
Another wiper device according to the present invention includes a pair of pivot holders each including a fitting portion that extends along a fitting axis, a pivot shaft that is rotationally supported by each pivot holder, and a frame that connects the pivot holders to each other. A plurality of recesses are formed in an outer side of each fitting portion. A wiper arm is secured to each pivot shaft. A receiving portion in which each fitting portion is received is formed at each end of the frame. The receiving portions are subjected to caulking with the fitting portions received in the corresponding receiving portions, such that a portion of each receiving portion that corresponds to each recess enters the recess. Each recess includes a curved bottom. Regarding each pivot holder, an angle between a normal line that corresponds to a maximum depth portion of each recess and a certain portion of a wall that forms the recess is defined as an open angle. Further, an angle between the axis of the corresponding pivot shaft and the normal line is defined as a shaft angle. In this case, each recess is shaped and located such that the open angle is constantly greater than zero and equal to or greater than the shaft angle, as viewed along any cross-sectional plane that includes the normal line.